A Somalian refugee who claims he was "possessed by the devil'' when he went on a frenzied knife-wielding rampage across Christchurch before being shot by police has today been jailed for six years and six months.

Zakariye Mohamed Hussein, 27, earlier admitted the violent March 15 attacks where he kidnapped and stabbed pie delivery driver Marteine Robin before knifing a city council worker.

At Christchurch District Court today he could not explain why he launched the "serious, unprovoked, gratuitous and random acts''.

Judge David Saunders told him his attacks terrified a number of innocent people who have suffered ongoing "physical and emotional harm'' and can no longer trust people.

"This was serious violence, involving the use of a weapon, and involving serious injuries,'' the judge told him.

Hussein has been in Hillmorton psychiatric hospital since the attacks recovering from his gunshot wounds and was earlier deemed fit to plead to the original charges.

He admitted charges of unlawful possession of a knife, kidnapping, and intent to cause grievous bodily harm. Police also withdrew a charge of attempting to kill the city council worker he kidnapped.

Defence counsel Allister Davis said his client wanted to issue a public apology to his victims today.

He was "full of remorse'', claiming he suffered "some sort of breakdown'' the night before, which led him to camping out at Redwood School overnight, armed with knives.

He's normally a "shy, reserved, polite'' man when on his medication but when, like on this occasion, doesn't take his drugs, says he is "possessed by the devil'', Mr Davis said.

Hussein can no longer lift or use the arm where he was shot by police, the lawyer said, but he accepts the police were right to do what they did.

He urged the judge to consider the man's background, where he and his family fled their homeland of Somalia when civil war broke out.

Hussein witnessed his uncle being shot dead, women violated, and lived with "bullets around every corner''.

The shooting drama started around 7am when he was disturbed in the grounds of Redwood School by caretaker, Noel Batstone.

He chased Mr Batstone and a teacher who barricaded themselves inside a classroom and phoned police.

She told him to "get the f*** out'' of her delivery truck, but he responded by forcing her at knifepoint to drive him across Christchurch, and then stabbing her in the shoulder.

"I feared the worst, I thought I was going to die,'' she said later that day.

Ms Robin eventually managed to escape when Hussein was momentarily distracted at a traffic jam almost one hour, and 50km later.

But the drama only escalated when Hussein, who arrived in New Zealand aged 18, left the truck near the busy intersection of Hoon Hay and Halswell roads and then almost fatally stabbed a Christchurch City Council worker, who has name suppression.

City construction worker Jade Lynn, 22, saw the attacker rampaging between vehicles and approached him with a crowbar, striking him in the neck, and herding him away from other members of the public.

Eyewitnesses described Mr Lynn as a "hero'' who prevented Hussein from attacking other bystanders.

Hussein only stopped when pepper sprayed, tasered and then shot twice by a female police officer in his shoulder and wrist.

Outside court, Mr Lynn was disappointed with the sentence of six and a half years with a minimum non-parole period of three years, three months.

"He should've got more, he stuffed my life up for a wee bit,'' said the man, who was praised by Judge Saunders for his "courageous actions'' that day for which he should be "publicly commended'' on.

Mr Lynn said he was proud to hear the judge's words.

"I hadn't done something good for a while.''

An emotional Mr Batstone spoke of his relief at seeing the man responsible for his sleepless nights get jailed.

Ms Robin, however, refused to speak to waiting media.

Asked for a comment, she said: "No, no. Honestly, no,'' before leaving with her daughter and friends.